U.S. patent application number 10/143846 was filed with the patent office on 2002-11-21 for image reading unit and image reading apparatus using the same.
Invention is credited to Sumiya, Osamu, Yui, Kenichi.
Application Number | 20020171880 10/143846 |
Document ID | / |
Family ID | 27346716 |
Filed Date | 2002-11-21 |
United States Patent
Application |
20020171880 |
Kind Code |
A1 |
Yui, Kenichi ; et
al. |
November 21, 2002 |
Image reading unit and image reading apparatus using the same
Abstract
An image reading unit includes an image sensor for converting
light from a document into an electric signal, and a circuit board
provided with the image sensor on one side. In the image reading
unit, a heat dissipating member for controlling a temperature of
the image sensor is attached to one side of the circuit board, and
a shield member for reducing a noise is provided on the other side
of the circuit board. The heat dissipating member and the shield
member are connected by a heat conductive member. Also, the heat
dissipating member is interposed between the image sensor and the
circuit board.
Inventors: |
Yui, Kenichi; (Kofu-shi,
JP) ; Sumiya, Osamu; (Kofu-shi, JP) |
Correspondence
Address: |
KANESAKA AND TAKEUCHI
1423 Powhatan Street
Alexandria
VA
22314
US
|
Family ID: |
27346716 |
Appl. No.: |
10/143846 |
Filed: |
May 14, 2002 |
Current U.S.
Class: |
358/505 |
Current CPC
Class: |
H04N 1/1013 20130101;
H04N 1/193 20130101; H04N 1/00989 20130101; H04N 2201/02468
20130101; H04N 2201/02456 20130101; H04N 2201/02485 20130101; H04N
1/03 20130101; H04N 1/00976 20130101; H04N 2201/02495 20130101 |
Class at
Publication: |
358/505 |
International
Class: |
H04N 001/46 |
Foreign Application Data
Date |
Code |
Application Number |
May 16, 2001 |
JP |
2001-146276 |
May 16, 2001 |
JP |
2001-146295 |
May 16, 2001 |
JP |
2001-146316 |
Claims
What is claimed is:
1. An image reading unit for reading an image on a document,
comprising: a circuit board, an image sensor mounted on one side of
the cicuit board for receiving light from the document and
converting the same into an electric signal, a heat dissipating
member disposed on said one side of the circuit board for
dissipating heat of the image sensor, a shield member disposed on
the other side of the circuit board for reducing a noise relative
to at least one of the image sensor and the circuit board, and a
heat conductive member situated between the heat dissipating member
and the shield member to transfer the heat from the heat
dissipating member to the shield member.
2. An image reading unit according to claim 1, wherein said heat
dissipating member is interposed between the image sensor and the
circuit board.
3. An image reading unit according to claim 2, wherein said circuit
board is provided with a through hole, and said heat conductive
member passes through the through hole of the circuit board to
thereby connect the heat dissipating member and the shield
member.
4. An image reading unit according to claim 1, wherein said shield
member includes a blacket adapted to fix the shield member to a
mounting member for the reading unit such that a position of the
shield member is freely adjustable.
5. An image reading apparatus comprising, said image reading unit
according to claim 1 and a light source for irradiating the light
to the document.
6. An image reading apparatus according to claim 5, further
comprising a platen for disposing the document, said reading unit
including said light source therein and moving along the platen,
said shield member being arranged in the image reading unit to
adjust a position thereof.
7. An image reading apparatus according to claim 5, further
comprising a platen for disposing the document, a stationary
support member for supporting the image reading unit, and a light
source unit having a light source therein and moving along the
platen, said shield member being arranged in the stationary support
member to adjust a position thereof.
8. An image reading apparatus according to claim 6, wherein said
circuit board is provide with a through hole, and said heat
conductive member passes through the through hole to connect the
heat dissipating member and the shield member.
9. An image reading apparatus according to claim 7, wherein said
circuit board is provide with a through hole, and said heat
conductive member passes through the through hole to connect the
heat dissipating member and the shield member.
Description
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
[0001] The present invention relates to an image reading unit and
an image reading apparatus using the same. More particularly, the
present invention relates to an image reading unit in which a
circuit board provided with an image sensor for reading an image
data, a heat dissipating member for controlling a temperature of
the image sensor is provided on one side of the circuit board, and
a shield member for reducing a noise is provided on the other side
and connected to the heat dissipating member via a heat conductive
member.
[0002] As shown in FIG. 16, a conventional image reading apparatus
for reading an image on a document with various sizes as an image
data includes a light source 86 for irradiating light to the
document; a plurality of reflecting mirrors 83, 84, 85 for
deflecting the light from the document; a condenser lens 87 for
condensing the light reflected by the reflecting mirrors 83, 84,
85; and an image sensor 80 for detecting the light from the
condenser lens 87. The light detected by the image sensor 80 is
subjected to the photoelectric conversion, and then processed as
the image data.
[0003] The image sensor for converting the received light into an
electric signal reads the image with timing in synchronization with
a clock signal with a predetermined frequency. Upon reading the
image signal from the image sensor, noises in a frequency band
including the clock signal frequency and frequencies with an
integral multiple of the clock frequency are generated.
[0004] Therefore, in order to prevent the noise from leaking
outside, for example, as disclosed in Japanese Patent Publication
(KOKAI) No. 05-347685 and Japanese Patent Publication (KOKAI) No.
08-32762, a shield cover made of a metal is provided for covering a
periphery of a circuit board.
[0005] However, the shield cover is provide to cover not only the
circuit board to which the image sensor is attached, but also a
larger area including a periphery of the circuit board and the
lens, resulting in a large shield cover. Thus, there has been an
example that the shield cover covers only the circuit board.
[0006] In general, as shown in FIG. 16, the image sensor 80 is
attached on the circuit board 81 such that a position of the image
sensor 80 with respect to an optical axis can be adjusted by screws
or the like. Then, the circuit board 81 provided with the image
sensor 80 is fixed to a frame 92 disposed in a chassis of an
apparatus main body by using a fixing member 90 such that the image
sensor can properly receive the light from the condenser lens 87. A
screw 91 fixes the circuit board 81 at a proper position with
respect to the condenser lens 87. Then, the shield cover 82 covers
the circuit board 81 in order to prevent the noise.
[0007] Further, since the image sensor is formed of several
millions of electric elements arranged on a silicon board to be a
large scale integrated circuit (LSI), a large amount of electricity
is consumed, and a heat generation rate per unit-hour becomes high.
Especially, in recent years, the number of pixels of the sensor in
the image reading apparatus has been steadily increased to achieve
a higher-density and higher-speed image reading. The clock speed
has been also accelerated in order to achieve higher-speed image
data transmission. Consequently, as the image sensor generates more
heat, a heat sink or heat dissipating plate needs to be attached to
an outline package of the image sensor in order to dissipate the
heat generated by the image sensor.
[0008] Therefore, in the conventional image reading apparatus, it
is necessary for the circuit board to separately provide with a
fixing and supporting member for attaching the circuit board to a
frame of the apparatus main body, a shield cover for preventing the
noise from entering the circuit board or shielding an external
noise, and a heat dissipating member (a heat sink member) for
dissipating the heat. Therefore, the number of parts increases, and
a manufacturing operation becomes cumbersome, resulting in a higher
manufacturing cost.
[0009] Also, a precise positioning is required for attaching the
circuit board to the frame of the apparatus main body, so that a
cumbersome adjustment operation is required.
[0010] The present invention has been made in view of the
aforementioned problems, and an object of the invention is to
provide an image reading unit and an image reading apparatus using
the same, in which an image sensor and a circuit board are attached
to a shield member for shielding and dissipating the heat, so that
the number of the parts and manufacturing cost can be lowered while
a position of the circuit board is easy to adjust.
[0011] Further objects and advantages of the invention will be
apparent from the following description of the invention.
SUMMARY OF THE INVENTION
[0012] To achieve the aforementioned object, the present invention
provides an image reading unit including an image sensor for
converting light from a document into an electric signal, and a
circuit board to which the image sensor is attached. In the image
reading unit, a heat dissipating member is disposed on one side of
the circuit board to control a temperature of the image sensor, and
a shield member is disposed at the other side of the circuit board
to reduce an electrical noise. A heat conductive member connects
the heat dissipating member and the shield member.
[0013] The heat dissipating member is interposed between the image
sensor and the circuit board, and a through hole is formed on the
circuit board. The heat conductive member is inserted into the
through hole of the circuit board to connect the heat dissipating
member and the shield member.
[0014] The image reading unit includes a mounting section for
fixing the shield member, so that the shield member equipped with
the image sensor, the heat dissipating member, and the circuit
board is attached to the mounting section to freely adjust a
position of the shield member.
[0015] Further, the present invention provides an image reading
apparatus, which includes a light source for irradiating light to a
document, an image sensor for converting the light from the
document into an electric signal, and a circuit board provided with
the image sensor. In the image reading apparatus, a heat
dissipating member for controlling a temperature of the image
sensor is disposed at one side of the circuit board, and a shield
member for reducing an electrical noise is disposed at the other
side of the circuit board. Then, the heat dissipating member and
the shield member is connected by a heat conductive member.
[0016] In the image reading apparatus of the invention, the light
source, the image sensor, the heat dissipating member, the circuit
board, and the shield member are mounted in an image reading unit
moving along the document. Then, the shield member attached with
the image sensor, the heat dissipating member and the circuit board
is attached to the image reading unit such that a position of the
shield member is freely adjustable.
[0017] Also, the light source is mounted on a light source unit
moving along the document. The image sensor, the heat dissipating
member, the circuit board and the shield member are mounted on a
stationary supporting member. Then, the shield member attached with
the image sensor, the heat dissipating member and the circuit board
is attached to the supporting member such that a position of the
shield member can be freely adjusted.
[0018] Further, a through hole may be formed on the circuit board,
and the heat conductive member is inserted into the through hole of
the circuit board, to thereby connect the heat dissipating member
and the shield member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a sectional view showing an image reading
apparatus according to an embodiment of the present invention;
[0020] FIG. 2 is an enlarged sectional view showing a portion of a
light source as an optical mechanism, a reflecting mirror section
as a light deflecting device, and a close contact type image sensor
as another optical reading device in the image reading apparatus
according to the embodiment of the present invention;
[0021] FIG. 3 is a perspective view of an appearance of an image
reading apparatus according to another embodiment of the invention,
in which a cover member provided with a platen glass for placing a
document thereon is attached;
[0022] FIG. 4 is a plan view showing an inside of the image reading
apparatus in FIG. 3;
[0023] FIG. 5 is a perspective view showing the inside of the image
reading apparatus in FIG. 3;
[0024] FIG. 6 is a perspective view of an image reading unit in the
image reading apparatus shown in FIG. 3, as seen from a rear side
thereof when the image reading unit is moving in an approach or
forward route for scanning the document;
[0025] FIG. 7 is another perspective view of the image reading unit
in the image reading apparatus shown in FIG. 3, as seen from a
front side thereof when the image reading unit is moving in the
approach or forward route for scanning the document;
[0026] FIG. 8 is a front view showing a state that a sensor board
equipped with an image sensor is attached to a shield member;
[0027] FIG. 9 is a perspective view showing the state that the
sensor board equipped with the image sensor is attached to the
shield member;
[0028] FIG. 10 is a sectional view showing a structure of the image
reading unit for reading the image shown in FIG. 3;
[0029] FIG. 11 is a perspective view showing the state that the
sensor board equipped with the image sensor is attached to the
shield member, as seen from a direction opposite to the direction
from which FIG. 9 is seen;
[0030] FIG. 12 is a side view of FIG. 11, as seen in a direction of
an arrow X in FIG. 11;
[0031] FIG. 13 is a perspective view showing a state of conductors
inside a flexible flat cable;
[0032] FIG. 14 is a perspective view showing a state of conductors
inside a layered flexible flat cable;
[0033] FIG. 15 is a sectional view of the layered flexible flat
cable; and
[0034] FIG. 16 is a schematic explanatory view showing a
conventional image reading apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0035] Hereunder, embodiments of the invention will be explained
with reference to the accompanying drawings.
[0036] The present invention provides an image reading unit and an
image reading apparatus using the same. The image reading unit is
applied to various types of copiers, facsimile machines, image
scanners connected to electronic appliances. Embodiments of the
invention show an example of the image reading apparatus for a
copier. In general, there are three types of image reading
apparatus as follows.
[0037] In the first type of the image reading apparatus, an image
reading unit formed of a lens and an image sensor is fixed to an
attaching section of the image reading apparatus. A light source
unit and a reflecting mirror unit are moved at a two to one speed
ratio along a platen so as to read an image on a document placed on
the platen.
[0038] In the second type of the image reading apparatus, an image
reading unit formed of a light source, reflecting mirrors, a lens
and an image sensor is fixed, and read an image on a document that
is moving along a platen.
[0039] In the third type of the image reading apparatus, an image
reading unit formed of a light source, reflecting mirrors, lens and
an image sensor is mounted to a carriage, and the carriage is moved
along a platen on which a document is placed.
[0040] Firstly, an embodiment in which the present invention is
applied to the first type of the image reading apparatus will be
explained.
[0041] FIG. 1 is a sectional view showing a structure of an image
reading apparatus according to an embodiment of the invention. FIG.
2 is an enlarged sectional view showing a portion including a light
source 110 as an optical mechanism section of the first image
reading section in the image reading apparatus, reflecting mirrors
12', 13', 14' as light deflecting means, and the second optical
reading device 40.
[0042] Incidentally, the copier according to this embodiment of the
invention has a function called ADF (automatic document feeder),
for feeding out the document consecutively and supplying the same
to the image reading section.
[0043] The image reading apparatus includes a lower unit 51' and an
upper unit 60 attached to the lower unit 51' by a hinge or the like
such that the upper unit 60 is freely capable of opening and
closing.
[0044] The upper unit 60 includes a housing 61 for accommodating a
transfer path in which the document is transferred, a pair of
rollers for transferring the document, and the second optical
reading device 40 for reading an image on a backside of the
document. In the housing 61, a document inlet 63 is formed in
correspondence with a sheet supply tray 52, and a document
discharge port is formed in correspondence with a sheet discharge
tray 64. The document introduced from the document inlet 63 is
transferred along the transfer path provided inside the housing,
and after a reading process is complete, the document is discharged
on the sheet discharge tray 64 through the document discharge
port.
[0045] Further, the first optical reading device 50 is provided for
reading an image on a front side of the document passing along a
sheet-through platen 66 provided along the transfer path. The first
optical reading device 50 is provided with a reduced optical system
sensor, and includes the first carriage 52' and the second carriage
53'. The carriages 52', 53' are driven by a motor, connected with
each other to maintain a predetermined distance between them, and
moved inside the unit in a right or left direction in FIG. 2.
[0046] As shown in FIG. 2, the carriage 52' is equipped with a
light source 110 for irradiating light to the document, and the
reflecting mirror 12'. The reflecting mirror 12' receives the light
from the document and reflects the light in a horizontal direction.
Also, the carriage 53' is equipped with the reflecting mirror 13'
for reflecting the light from the reflecting mirror 12' toward a
vertical direction, and the reflecting mirror 14' for reflecting
the light from the reflecting mirror 13' in a horizontal direction
opposite to the reflected light from the reflecting mirror 12'.
[0047] The first optical reading device 50 fixed inside the lower
unit 51' includes a condenser lens 15 for receiving the light from
the reflecting mirror 14'; an image sensor 16 for receiving the
light focused by the condenser lens 15; a heat sink member 72 for
controlling a temperature of the image sensor 16; and a circuit
board 73 attached to the image sensor 16 through the heat sink
member 72. The light detected by the image sensor 16 is converted
into a digital signal by the circuit board 73, and then sent to an
interface board inside the copier through a control board that
carries out various image processing. The heat sink member 72 and
the circuit board 73 are fixed to a shield member 70', which has
both the heat sink function and the noise shield function, by a
heat conductive member 95. The shield member 70' is fixed to an
attaching section 76, to thereby form the image reading unit.
[0048] In the embodiment of the invention, the first optical
reading device 50 includes a platen (referred to as "book platen"
hereinafter) 55'. The book platen 55' is disposed on an upper
surface of the lower unit 51' adjacent to the sheet-through platen
66 for placing the documents thereon. The document placed on the
book platen 55' is scanned by moving the carriages 52', 53', to
thereby read the image on the document.
[0049] The carriages 52', 53' are respectively driven by the motor,
and interlock with each other to maintain the predetermined
distance between them. The carriage 53' moves with one to two ratio
to the carriage 52' inside the lower unit 51' in the right or left
direction in FIG. 2.
[0050] As shown in FIG. 2, in the second optical reading device 40,
attached to a shield cover for reducing a noise and integrally
fixed to the second optical reading device 40 are a light source
112 for irradiating light for reading an image on the backside (a
surface facing upward) of the document transferred in the transfer
path; a contact glass 67 through which the light from the light
source 112 and the rear surface of the document passes through; a
SELFOC lens 68 for changing the reflected light into parallel
light; a line image sensor 69 for detecting the light through the
SELFOC lens 68 and converting the light into an electric signal;
and the circuit board 41. The light detected by the image sensor 69
is converted into the digital signal by the circuit board 41, and
sent to the interface board inside the copier through the image
processing board provided inside the lower unit 51'.
[0051] Next, according to another embodiment, an image reading unit
2 and an image reading apparatus of the invention applied to the
third type of the image reading apparatus will be explained. As
described above, in the third type of the image reading apparatus,
the image reading unit 2 formed of a light source, reflecting
mirrors, a lens and an image sensor is moved along a platen on
which a document is placed to thereby read an image on the
document.
[0052] FIG. 3 is a perspective view showing an image reading
apparatus having a cover member 101 disposed on an upper surface of
the main body frame 1 and a platen glass 9 for placing the document
thereon. FIG. 4 is a plan view showing an inside structure of the
image reading apparatus, and FIG. 5 is a perspective view showing
the inside structure of the image reading apparatus in a state that
the image reading unit 2 is at a home position. FIG. 6 is a
perspective view of the image reading unit 2 as seen from a rear
side in a state that the image reading unit is moving along a path
while scanning the document image. FIG. 7 is another perspective
view of the image reading unit 2 as seen from a front side in a
state that the image reading unit is moving along a path while
scanning the document image. Incidentally, an arrow A in FIGS. 5 to
7 indicates a moving direction of the image reading unit 2 when the
image reading unit 2 reads the image on the document (a forward
movement). FIG. 8 is a front view showing a sensor board 32 with an
image sensor 31 attached to a shield member 70. FIG. 9 is a
perspective view showing a sensor board 32 with an image sensor 31
attached to the shield member 70. FIG. 10 is a sectional view
showing a structure of the image reading unit 2 for reading the
image on the document. FIG. 11 is a perspective view seen from a
direction opposite to the direction of the view in FIG. 9, and FIG.
12 is a side view of FIG. 11 as seen in a direction of an arrow X
in FIG. 11.
[0053] The document is placed on the platen glass 9 disposed on the
cover member 101 of the main body frame 1 shown in FIG. 3 such that
the image surface of the document faces downward. As shown in FIGS.
4 and 5, below the platen glass 9, the image reading unit 2 is
guided by a guide rod 3 and a guide rail 4, which are provided in
the main body frame 1 as guiding means, and is driven by a stepping
motor 5 connected through a driving belt 10 to slide along the
platen glass 9 back and forth. Accordingly, the image reading unit
2 reads the image on the document while moving (the forward
movement) in the direction shown by the arrow A in FIG. 5.
[0054] Here, in the image reading apparatus according to the
embodiment of the invention, a configuration of the image reading
unit 2 for reading the image on the document will be explained.
[0055] As shown in FIG. 10, the image reading unit 2 is provided
with a mold frame 26. The mold frame 26 is provided with a light
source 6, such as a xenon lamp, for irradiating light to the
document; a reflecting plate 29 for reflecting the light from the
light source 6 toward the surface of the document; reflecting
mirrors 20, 21, 22, 23, 24 receiving the light from the document
and providing the same in a horizontal direction; a lens unit 27
for condensing or focusing the light from the reflecting mirror 24;
the image sensor 31, such as CCD, as an optical element for
receiving the light focused by the lens unit 27; the sensor board
32 for mounting the image sensor 31; and a semiconductor 28 fixed
on the sensor board 32. Incidentally, between the reflecting mirror
20 for reflecting the light first and the reflecting mirror 24 for
reflecting the light last, a shooting plate 34 for averaging light
intensity in an entire reading width is attached by a screw 35 such
that the position of the shooting plate 34 can be adjusted. Also,
as shown in FIG. 6, the light source 6 is disposed at one end of
the image reading unit 2 in the forward movement direction. The
shield member 70 provided with the sensor board 32 is fixed to the
mold frame 26 of the image reading unit 2 at the other end of the
image reading unit 2 in the forward movement direction.
[0056] Operations of reading the image on the document are
performed as follows. First, the light reflected from the document
in a vertical direction is irradiated to the reflecting mirror 20.
Then, the light reflected from the reflecting mirror 20 in a
substantially horizontal direction is reflected by the reflecting
mirror 21 toward a substantially vertical direction. The reflecting
mirror 22 receives the light reflected by the reflecting mirror 21
in the substantially vertical direction, and reflects the light in
a substantially vertical direction toward a horizontal direction
opposite to that of the reflected light from the reflecting mirror
20. The reflecting mirror 23 receives the light reflected by the
reflecting mirror 22 in the horizontal direction, and reflects the
received light toward a substantially vertical direction opposite
to that of the reflected light from the reflecting mirror 21. The
reflecting mirror 21 receive the light reflected from the
reflecting mirror 23 in the substantially vertical direction, and
reflects the received light toward a substantially horizontal
direction opposite to that of the reflected light from the
reflecting mirror 20.
[0057] The reflecting mirror 20 receives the reflected light from
the reflecting mirror 21 in the substantially horizontal direction,
and reflects the received light toward a substantially vertical
direction opposite to that of the reflected light from the
reflecting mirror 23 in a substantially vertical direction. The
reflecting mirror 24 receives the light reflected by the reflecting
mirror 20 in the substantially vertical direction, and reflects the
received light toward a horizontal direction opposite to that of
the reflected light from the reflecting mirror 21.
[0058] The light reflected from the reflecting mirror 24 enters the
lens unit 27 to be focused, and the light focused by the lens unit
27 enters the image sensor 31 of an optical element.
[0059] The light detected by the image sensor 31 is converted into
a digital signal by an analog-front-end device (hereinafter
referred to as "AFE"), which is provided on the sensor board 32 to
process the analog signal. The light converted into the digital
signal is sent to an interface board in a higher level apparatus,
such as a copier, through the control board 100 (refer to FIG. 4)
that operates various types of image processing. As described
above, the image reading apparatus is structured to create a clear
and sharp image at a focal point of the lens by reflecting the
image light several times.
[0060] In the image reading apparatus structured as described
above, in order to prevent functional deterioration due to heat
from the image sensor 31, it is necessary to dissipate the heat
generated by the image sensor 31. Further, it is necessary to
prevent electromagnetic waves radiated by a power supply and a
cable from affecting the image sensor 31.
[0061] If the focal point of the lens unit 27 is not accurately
located at the image sensor 31, which receives the light from the
reflecting mirror 24, a fine image data can not be obtained.
Therefore, in order to obtain the fine image data, it is required
to be able to adjust the position accurately, and preferably the
adjustment is easy. To achieve the goal, it is preferable that the
number of parts for fixing the sensor board 32 to the attaching
section is small.
[0062] Therefore, in the present embodiment, the sensor board 32
with the image sensor 31 is fixed to the shield member 70 that
reduces the noise. The shield member 70 is fixed to an attaching
section 26a (refer to FIGS. 11 and 12) attached to the mold frame
26 of the image reading unit 2 such that the position of the shield
member can be freely adjusted.
[0063] The shield member 70 is made of a non-magnetic metal, such
as a copper or aluminum, with high heat dissipating property, or a
magnetic metal such as an iron or nickel.
[0064] As shown in FIG. 6, the shield member 70 is attached to the
mold frame 26 of the image reading unit 2.
[0065] In the present invention, as shown in FIGS. 8 and 9, the
image sensor 31 is attached to the sensor board 32a with a heat
sink member 78 in between, which is provided for preventing over
heat of the image sensor 31 and formed of a metal, such as a
copper, aluminum, iron or nickel. Then, as shown in FIG. 11, a
metallic screw 77 engages a screw hole 78a of the heat sink member
78 through a hole 76a formed at an outer attaching section 76 of
the shield member 70, so that the sensor board 32 is fixed to the
shield member 70.
[0066] Then, the heat conducted to the heat sink member 78 from the
image sensor 31 through the screw 77 is further conducted to the
shield member 70 to be dissipated. As described above, since the
shield member 70 is formed of the member having the high heat
dissipating property, such as a metal plate, the shield member 70
itself has a high heat dissipating property. Therefore, the shield
member 70 can act as a heat sink to prevent the functional
deterioration of the image sensor by dissipating the heat generated
from the image sensor 31.
[0067] Also, as shown in FIGS. 11 and 12, a bracket 75 of the
shield member 70 is provided with a mounting hole 74 for fixing the
shield member 70 to the mold frame 26 of the image reading unit 2,
and a screwdriver hole 79 facing the mounting hole 74. The mounting
hole 74 is elongated in an optical axis direction such that the
shield member 70 can be moved for adjusting the optical axis
direction of the lens unit. The mounting hole 74 and the attaching
section 26a of the mold frame 26 of the image reading unit 2 are
connected by a connecting member 74a, such as a screw, so that the
shield member 70 is fixed to the mold frame 26. Further, a screw
driver can be inserted through a screwdriver hole 79 from above the
image reading unit 2 to rotate the connecting member 74a, so that
the position of the shield member 70 can be adjusted.
[0068] As shown in FIGS. 9, 11 and 12, regarding the heat sink
structure, the heat sink member 78 is interposed between the image
sensor 31 and the sensor board 32, and the image sensor 31 is fixed
to the sensor board 32. Also, a heat conductive member, such as the
metallic screw 77, is inserted into a through hole 32a of the
sensor board 32 from outside the shield member 70, and is screwed
with the screw hole on the heat sink member 78, so that the sensor
board 32 is fixed to the shield member 70. Therefore, the heat,
which is conducted to the heat sink member 78 from the image sensor
31, is conducted to the shield member 70 through the screws 77 and
dissipated, to thereby prevent the image sensor 31 from over
heating, as well as an influence of the heat on the sensor board
32.
[0069] Also, in adjusting the optical axis direction of the lens
unit 27, if the connecting member is a screw, the fixed screw is
loosened and the shield member 70 is shifted in a right or left
direction of the mounting hole 74 for fine adjustment. As described
above, since the image sensor 31 and the sensor board 32 are
integrally fixed to the shield member 70, the adjustment can be
made by just changing the mounting position of the shield member
70.
[0070] The shield member 70 and the attaching section 26a of the
mold frame 26 of the image reading unit 2 are connected by a
connecting member to secure the connection in an accurate position
without any shifts. The attaching section 26a of the mold frame 26
in the image reading unit 2 is fixed to the bracket 75 of the
shielding member 70 by a connection member, like a screw and a
washer, so as not to be shifted.
[0071] Incidentally, in the present invention, the mounting hole 74
of the shield member 70 has a shape allowing the position
adjustment. However, the mounting hole 74 of the shield member 70
may be a round hole in which the screw is inserted, and the
attaching section of the mold frame of the image reading unit 2 may
be a mounting hole having a shape that allows the position
adjustment.
[0072] As shown in FIGS. 4 and 5, the image reading unit 2 of the
embodiment as described above is guided by the guiding means (the
guide rod 3 and the guide rail 4), and driven the driving belt 10
connected to the stepping motor 5 to move back and forth. A light
source cable 7 for supplying an electric power to the light source
6 and a signal cable 8 for transmitting the input/output data of
the sensor board 32 are connected to the image reading unit 2.
Since the light source cable 7 carries a high voltage current, a
flexible electric wire is used for the light source cable. A
flexible flat cable is used for the signal cable 8.
[0073] Now, the signal cable 8 will be explained.
[0074] FIG. 13 is a perspective view showing conducting paths
inside the signal cable 8. FIG. 14 is a perspective view showing a
state that the signal cables 8 are layered. FIG. 15 is a sectional
view of the layered signal cable 8.
[0075] The signal cable 8 is formed of a flexible flat cable
(hereinafter referred to as "FFC") in which an input cable and an
output cable are laminated and integrally formed. The signal cable
8 is provided for wiring between the sensor board 32 and the
control board 100 to thereby send and receive the signal. In the
case that the AFE is provided in the sensor board 32 as in the
embodiment of the invention, the signals transmitted through the
FFC are the control signal for the image sensor 31 and AFE and the
digital output signal from the AFE. In the case that the AFE is
provided in the control board 100, the signals transmitted through
the FFC are the control signal for the image sensor 31 and the
analog output signal from the image sensor 31. A long FFC is used
for wiring between the boards 32 and 100, since these boards are
separated and the image reading unit moves back and forth. A FFC
used for the signal cable 8 has a width of about 30 mm, and signal
paths and ground paths are arranged side by side.
[0076] In the FFC, a copper foil is used as a conducting member,
which is covered by a non-conductive resin, such as a polyimide.
Also, as a reinforcement, a polyester film is attached to a rear
surface of the FFC, and a thickness of the polyester film is in a
range from about 0.05 mm to 0.6 mm, and the polyester film is about
0.6 mm in thickness in the embodiment. The FFC is not rigid, thus
the vibration due to a motion of the cable itself is unlikely to be
transmitted to other devices. For this reason, the FFC has been
used as the signal cable in the image reading apparatus.
[0077] Since a large number of the signals described above are
created at a frequency in a range of several MHz to several tens
MHz, harmonic a little higher than the signal has a shorter
wavelength. When a wavelength is equal to a length of the FFC, a
resonance occurs. When several tens percent of the wavelength
becomes less than the length of the FFC, a high-level
electromagnetic noise is generated.
[0078] As a method for preventing the electromagnetic field, it has
been known that a return path of a reflux current and the signal
path are paired and close to each other so as to minimize a loop
area of the return path. Alternatively, a shield member covering
the entire surface of the FFC as a ground point can prevent the
electromagnetic field. However, in the image reading apparatus of
the embodiment, such a shield member deteriorates bending
durability and increases a cost, thus is not practical.
[0079] As shown in FIG. 13, in a conventional method of arranging
the signal paths in the FFC, the signal paths and the ground paths
are arranged alternately such that conductors 41, 43, 45, . . .
constitute the signal paths (the signal lines), and conductors 42,
44, 46, . . . constitute the ground paths (the ground lines).
Accordingly, the return paths, that are a pair of the signal paths
and ground paths, are disposed close to the respective signal
paths, to thereby reduce the loop area.
[0080] This method is effective for EMC (Electromagnetic
Compatibility) with respect to the flat cable, such as FFC. In the
case that the number of the paths in the FFC is limited, every two
signal paths are arranged to have one ground path alternately. In
other words, each ground path is arranged at an interval of two
adjacent signal paths, such that the conductors 41, 42, 44, 45, . .
. constitute the sending paths (the signal lines), and the
conductors 43, 46, . . . constitute the ground paths (the ground
lines). Accordingly, the EMC can be improved.
[0081] Further, in the image reading apparatus of the embodiment,
in order to provide a more effective EMC countermeasure, as shown
in FIG. 14, a plurality of the FFC, for example, a FFC 51 and a FFC
52 are laminated. In the FFC 52, the signal paths and the ground
paths are shifted such that conductors 53, 56, 57, 60, . . .
constitute the signal paths (the signal lines), and conductors 54,
55, 58, 59, . . . constitute ground paths (the ground lines). In
this case, the signal lines and ground lines are alternately
opposed to each other between the FFC 51 and the FFC 52 in at least
a part of the cable lines FFC 51 and FFC 52. Therefore, the number
of the ground paths adjacent to the signal paths is increased.
[0082] Accordingly, the configuration described above makes it
possible to reduce the number of the ground paths in the FFC to
thereby reduce the width of the FFC. If the signal paths and ground
paths are arranged in a conventional way, the signal paths in the
FFC 51 and the signal paths in the FFC 52 would be in the same
rows. However, in the embodiment, the signal paths in the FFC 51
and the signal paths in the FFC 52 are shifted with each other, and
the ground paths in the FFC 51 and the ground paths in the FFC 52
are shifted with each other. Accordingly, the returns paths are
created close to the signal paths between the FFCs.
[0083] As a result, the magnetic flux is reduced more effectively,
to thereby further prevent the magnetic field from being generated.
Also, a characteristic impedance of the conductor can be improved,
so that the EMC performance can be improved, and signal distortion
can be reduced.
[0084] As shown in FIG. 15, the FFC has a width of the conductor W,
a thickness of the conductor t, a thickness of the insulation d and
a pitch p. In this case, in addition to the ground path at a
distance (p-W) with a width d, the ground path is positioned at a
distance (2.times.d) with a width W. For example, the ground path
55 has the distance (p-W) and width t with respect to the signal
path 53 in the FCC 51. In addition, the ground path 54 in the FCC
52 has the distance (2.times.d) and the width W with respect to the
signal path 53.
[0085] As an example of the image reading apparatus, a FCC with the
conductor width 0.6 mm, the conductor thickness 0.1 mm, the
insulation thickness 0.1 mm, and the pitch 1 mm is used to connect
the image sensor board and the control board 100. In this case, the
signal path and the ground path in the same FCC are situated with a
distance 0.4 mm and a width 0.1 mm. The signal path and the ground
path in the different FCCs are situated with a distance 0.2 mm and
a width 0.6 mm. In other words, in the flat cables, the distance
between the paths in the different FCCs is shorter than that in the
same FCC.
[0086] Therefore, the ground path can be disposed much closer to
the signal path. Since a return current flows selectively in the
path closest to the signal path, in the case of using the laminated
FFC, the return current from the signal path in one FFC flows the
path in the other FFC. Accordingly, the loop area is effectively
reduced to prevent the electromagnetic field generated from the
FFC. At the same time, the characteristic impedance of the
conductor can be improved, so that the EMC performance can be
improved, and the signal distortion can be reduced.
[0087] Also, in the case that the AFE is disposed in the image
sensor board, as more than 30 sending and receiving signals are
transmitted between the image sensor board and the control board
100, the FFC needs to have a little over 30 mm width to accommodate
more than 30 paths. In that case that the AFE is not disposed in
the image sensor board, as more than 10 sending and receiving
signals are transmitted between the image sensor board and the
control board 100, the FFC needs to have a little over 10 mm width
for more than 10 paths to improve the EMC. Incidentally, the
thickness of this FCC becomes double, about 0.6 mm.
[0088] Also, as another example, a FCC with the conductor width 0.3
mm, the conductor thickness 0.05 mm, the insulation thickness 0.1
mm, and the pitch 0.5 mm is used to connect the image sensor board
and the control board 100. In this case, the signal path and the
ground path in the same FCC are situated with a distance 0.2 mm and
a width 0.05 mm. The signal path and the ground path in the
different FCCs are situated with a distance 0.2 mm and a width 0.3
mm. Accordingly, the ground path can be disposed much closer to the
signal path.
[0089] Since the return current flows selectively in the path
closest to the signal path, in the case of using the laminated FFC,
the return current from the signal path in one FFC flows the path
in the other FFC. Accordingly, the loop area is effectively reduced
to prevent the electromagnetic field from being generated from the
FFC. At the same time, the characteristic impedance of the
conductor can be improved, so that the EMC performance can be
improved, and the signal distortion can be reduced. The level of
emitting the electromagnetic noise can be reduced lower than a
predetermined level.
[0090] Also, in the case that the AFE is disposed in the image
sensor board, as more than 30 sending and receiving signals are
transmitted between the image sensor board and the control board
100, the FFC needs to have a little over 15 mm width to accommodate
more than 30 paths. In that case that the AFE is not disposed in
the image sensor board, as more than 10 sending and receiving
signals are transmitted between the image sensor board and the
control board 100, the FFC needs to have a little over 5 mm width
for more than 10 paths to improve the EMC. Incidentally, the
thickness of this FCC becomes double, about 0.6 mm.
[0091] As described above, in the embodiment of the invention, the
signal cable is formed of a plurality of flat cables, and the
signal paths and the ground paths in the cables are arranged such
that each signal path in the laminated flat cables is surrounded by
the ground paths.
[0092] Accordingly, the level of emitting the electromagnetic noise
can be reduced to a predetermined level or less, and the image data
read by the image sensor is not distorted in the image reading
apparatus of the invention.
[0093] Now, an arrangement of the light source cable 7 to be
connected to the image reading unit 2 and the signal cable 8
described above will be explained.
[0094] The light source cable 7 connected to the light source 6 and
the signal cable 8 connected to the sensor board 32 are
respectively drawn from both end sides of the image reading unit 2
in a direction perpendicular to the moving direction of the unit
toward opposite directions.
[0095] As shown in FIG. 4 and FIG. 7, the light source cable 7
extends from the light source 6 to the central portion of the guide
rod 3, and is connected to a power supply 12 through light source
cable fixing means 11, such as a metal binding, provided in the
central portion of the guide rod 3. One end of the light source
cable 7 is bent in a U-shape and connected to the light source 6
from a rear end of the image reading unit 2 in the scanning
direction.
[0096] The light source 6 is a discharge type and an elongated
rod-like light source, and a high voltage (a several thousands
volt) is applied thereto. Accordingly, the light source cable 7 has
a thick cover to withstand the high voltage.
[0097] As shown in FIG. 7, the light source cable 7 is drawn toward
the rear side of the image reading unit 2 in the moving direction
(the direction of arrow A in the figure). When the image reading
unit 2 is moved to read the image on the document, the light source
cable 7 is accompanied with the image reading unit 2 with shifting
a bent point of the U-shaped portion.
[0098] The signal cable 8 structured as described above is drawn
from the sensor board 32 toward the moving direction through a
backside of a light source support section 13 as shown in FIG. 7.
The signal cable 8 drawn from the unit 2 is accompanied with the
image reading unit 2 when the unit 2 is moving. Incidentally, as
shown in FIG. 8, the signal cable 8 is pressed and fixed by the
guide rail 4 at the central portion of the moving range of the
image reading unit 2. When the image reading unit 2 is moved to
read the image on the document, the signal cable 8 is moved in the
moving direction of the unit with the image reading unit 2. The
signal cable 8 is moving from a signal cable fixed portion 8a at
the central portion of the moving range of the image reading unit 2
with shifting a bent point of a U-shaped portion.
[0099] At this time, the bent point of the U-shaped portion of the
cable 8 shifted by the movement is held by the light source support
section 13 so as to keep the cable from touching the platen glass
9.
[0100] Then, as shown in FIG. 7, the signal cable 8 is drawn from
the sensor board 32 in the moving direction under the light source
support section 13. Thus, the light source support section 13 can
hold the bending point of the cable 8 when the image reading unit 2
is moved to read the image on the document.
[0101] Since the signal cable 8 is pressed and fixed by the guide
rail 4 at the center portion of the main body frame 1 of the image
reading apparatus, on which the image reading unit 2 is placed, the
length of the signal cable 8 can be a half of the distance in which
the image reading unit 2 is moved for reading the image. Therefore,
the length of the signal cable 8 can be shortened, and a load
applied to the image reading unit 2 with moving back and forth can
be reduced. Also, it is unlikely for the signal cable 8 to loosen
to cause a problem. Further, since the length of the signal cable 8
is relatively shorter, it is harder to be affected by the
noise.
[0102] Here, the light source cable 7 is drawn from the image
reading unit 2 toward the rear side in the moving direction (the
direction of the arrow A) of the unit 2, and bent in the U-shape.
Then, the light source cable 7 is supported by the fixing means 11,
and the bent point of the light source cable 7 is gradually shifted
as the image reading unit 2 is moved to scan the image. If the
light source cable 7 is not flexible, the bent point of the cable
becomes large, so that the cable 7 touches the platen glass 9,
resulting in causing wear of the cable. Also, the movement of the
image reading unit 2 is impaired.
[0103] Therefore, in the present invention, the direction of
drawing out the light source cable 7 is arranged to be opposite to
that of the signal cable 8. The light source cable 7 is drawn out
from the unit 2 in the direction opposite to the scanning direction
(direction of the arrow A) of the image reading unit 2, and bent in
the U-shape at the rear side of the image reading unit 2.
[0104] Since the bent point of the light source cable 7 is located
at the rear side of the image reading unit 2 in the moving
direction of the image reading unit 2, the bent point of the cable
7 is pressed by the image reading unit 2, to thereby prevent from
enlarging. Therefore, the aforementioned problems due to an
enlarged bent point can be prevented.
[0105] The arrangement of the light source cable 7 and the signal
cable 8 of the image reading unit 2 has been explained. In order to
read an accurate image, it is necessary to move the image reading
unit 2 accurately.
[0106] Namely, as described above, the light source cable 7 is
drawn from the image reading unit 2 to the rear side in the moving
direction (the direction of the arrow A), and bent in the U-shape
and fixed by the fixing means 11. When the image reading unit 2 is
moved to scan, the bent point is gradually shifted in the light
source cable 7. If the light source cable 7 is not flexible, the
bent point becomes large, thus the light source cable 7 touches the
platen glass 9, interfering the movement of the image reading unit
2.
[0107] Also, in the case that the light source cable 7 is located
at only one side with respect to the moving direction of the image
reading unit 2, the load to the image reading unit 12 is different
from the other side, so that the moving speed is changed
respectively at each side to cause an uneven image.
[0108] To prevent this, there is an example that the light source
cable 7 is divided into a plurality of cables, and they are
disposed at both right and left sides with respect to the central
portion of the image reading unit 2. In this example, the drawing
out direction of the respective cables from the image reading unit
2 is the same. In the case that the cables having a different
thickness, or a different stiffness are used, a curvature of the
U-shaped bent portion of the cable on the right side is different
from that of the cable on the left side, so that the resistance
against the reading unit is different, resulting in an unstable
moving speed.
[0109] Thus, in the present invention, the direction of drawing out
the light source cable 7 from the unit 2 is arranged to be opposite
to that of the signal cable 8, to thereby eliminate the
aforementioned problem, that is, the unstable moving speed. The
light source cable 7 is drawn out from the image reading unit 2 in
the direction opposite to the moving or scanning direction of the
image reading unit 2, and is bent in the U-shape at the rear side
of the moving direction of the image reading unit 2
[0110] The signal cable 8 passes through a side under the light
source 6 of the image reading unit 2, and is drawn out in the
moving direction of the image reading unit 2. Then, the signal
cable 8 is bent in the U-shape at a forward side of the fixed
section 8a provided at the central portion of the moving range of
the image reading unit 2 in the moving direction.
[0111] As described above, the position and the direction of the
bent point of the cables are opposite to each other, so that the
running load applied to the image reading unit 2 is spread. Then,
since the respective cables are disposed away from each other at
the both end sides of the image reading unit 2, radio wave noises
from them do not affect with each other.
[0112] Also, the signal cable 8 is connected to the control board
100 extending from the fixed section 8a at the central portion of
the moving range of the image reading unit 2, obliquely crossing
through the frame 1, and crossing the light source cable 7. As
described above, since the signal cable 8 crosses perpendicularly
to the light source cable 7, the signal cable 8 is not affected by
the noise emitted from the light source cable 7.
[0113] Furthermore, the signal cable 8 and the light source cable 7
are fixed at the central portion of the moving range of the image
reading unit 2. Since both the cables are connected from the fixed
connection portions of the image reading unit 2, the length of each
cable is about a half of the moving range of the image reading unit
2. According to the structure of the cables in the invention, since
the length of the cable accompanied with the movement of the unit
is relatively short, the load applied to the movement of the unit
can be minimized.
[0114] Also, since the length of the cable is short, when the bent
portions of the signal cable 8 and the light source cable 7 are
shifted in the cables 7 and 8 as the image reading unit 2 is moved,
the signal cable 8 and the light source cable 7 are not twisted.
Also, the bent portions are prevented from expanding upwardly.
[0115] As described above, in the present embodiment, the light
source is disposed at one end in the moving direction of the
reading unit, and the image sensor is disposed at the other end. In
addition, the light source cable connected to the light source and
the signal cable connected to the image sensor are respectively
drawn from two different ends. Therefore, the running load between
right and left sides of the moving direction of the image reading
unit can be balanced. Further, the light source cable and the
signal cable are drawn from the directions opposite to each other
along both ends of the moving direction of the unit, to thereby
maintain the load balance between the left and right sides of the
moving direction of the unit. Accordingly, the image reading unit
and the image reading apparatus can achieve the high-density and
high-speed image reading.
[0116] Further, in the image reading apparatus of the invention,
since the signal cable 8 and the light source cable 7 are disposed
away from each other at both sides of the main body frame, the
electric wave emitted from the one cable does not interfere with
the other, and the signal cable 8 is not effected by the electric
wave hindrance, such as noises.
[0117] Also, the signal cable 8 is drawn from the main body frame
to cross perpendicular to the light source cable 7. Thus, the radio
waves from the cables do not interfere with each other.
[0118] As described above, in the image reading unit 2 of the
invention, the shield member 70 equipped with the image sensor 31,
the heat sink member 78, and the sensor board 32 is provided with
the bracket 75. The mounting hole 74 formed on the bracket 75 and
the attaching section 26a of the mold frame 26 of the image reading
unit 2 are fixed by the connecting member 74a such that the
position thereof can be freely adjusted.
[0119] As described above, the shield member 70 for fixing the
sensor board 32 to the image reading unit 2 reduces the noise, and
also acts as the heat sink for dissipating the heat generated from
the image sensor 31. Therefore, the number of parts can be reduced,
and a manufacturing cost can be lowered.
[0120] While the invention has been explained with reference to the
specific embodiments of the invention, the explanation is
illustrative and the invention is limited only by the appended
claims.
* * * * *